Films of Bare Single-Walled Carbon Nanotubes from Superacids with Tailored Electronic and Photoluminescence Properties

The use of single-walled carbon nanotubes (SWCNTs) in fabricating macroscopic devices requires addressing the challenges of nanotube individualization and organization in the desired functional architectures. Previous success in depositing bare SWCNTs from chlorosulfonic acid onto silicon oxide microporous and mesoporous nanoparticles has motivated this study of their deposition onto fused silica substrates. A facile dip-coating method is reported that produces thin homogeneous films in which the carbon nanotubes are not covered by surfactants or shortened by sonication. Photophysical, electrical, chemical, and morphological properties of these SWCNT films have been characterized. When prepared at low densities, the films exhibit near-IR photoluminescence from individualized SWCNTs, whereas when prepared at high densities the films behave as transparent conductors. Sheet resistance of 471 ohm/sq has been achieved with film transmittance of ∼ 86%

Understanding Charge-Transfer Characteristics in Crystalline Nanosheets of Fullerene/(Metallo)porphyrin Cocrystals

Cocrystals in the form of crystalline nanosheets comprised of C₇₀ and (metallo)­porphyrins were prepared by using the liquid–liquid interfacial precipitation (LLIP) method where full control over the morphologies in the C₇₀/(metallo)­porphyrins nanosheets has been accomplished by changing the solvent and the relative molar ratio of fullerene to (metallo)­porphyrin. Importantly, the synergy of integrating C₇₀ and (metallo)­porphyrins as electron acceptors and donors, respectively, into nanosheets is substantiated in the form of a near-infrared charge-transfer absorption. The presence of the latter, as reflection of ground-state electron donor–acceptor interactions in the nanosheets, in which a sizable redistribution of charge density from the electron-donating (metallo)­porphyrins to the electron-accepting C₇₀ occurs, leads to a quantitative quenching of the localized (metallo)­porphyrin fluorescence. Going beyond the ground-state characterization, excited-state electron donor–acceptor interactions are the preclusion to a full charge transfer featuring formation of a radical ion pair state, that is, the one-electron reduced fullerene and the one-electron oxidized (metallo)­porphyrin

Increased Solubility, Liquid-Crystalline Phase, and Selective Functionalization of Single-Walled Carbon Nanotube Polyelectrolyte Dispersions

The solubility of single-walled carbon nanotube (SWCNT) polyelectrolytes [K(THF)]_<i>n</i>SWCNT in dimethyl sulfoxide (DMSO) was determined by a combination of centrifugation, UV–vis spectral properties, and solution extraction. The SWCNT formed a liquid crystal at a concentration above 3.8 mg/mL. Also, crown ether 18-crown-6 was found to increase the solubility of the SWCNT polyelectrolytes in DMSO. Raman spectroscopy and near-infrared (NIR) fluorescence analyses were applied to study the functionalization of SWCNTs. Small-diameter SWCNTs were found to be preferentially functionalized when the SWCNT polyelectrolytes were dispersed in DMSO

Macroscopic Nanotube Fibers Spun from Single-Walled Carbon Nanotube Polyelectrolytes

In this work, single-walled carbon nanotube (SWCNT) fibers were produced from SWCNT polyelectrolyte dispersions stabilized by crown ether in dimethyl sulfoxide and coagulated into aqueous solutions. The SWCNT polyelectrolyte dispersions had concentrations up to 52 mg/mL and showed liquid crystalline behavior under polarized optical microscopy. The produced SWCNT fibers are neat (<i>i</i>.<i>e</i>., not forming composites with polymers) and showed a tensile strength up to 124 MPa and a Young’s modulus of 14 GPa. This tensile strength is comparable to those of SWCNT fibers spun from strong acids. Conductivities on the order of 10⁴ S/m were obtained by doping the fibers with iodine